The present invention particularly relates to process for regenerating adsorption systems employed for desulfurizing exhaust gas from, for example, a steam power plant and the like. Efficiency of operation and reduced manufacturing costs are of importance in such systems.
It is known to remove contaminants such as sulfur dioxide from exhaust gases with the use of active carbon or other similar adsorbents, and further to regenerate the adsorbents with for example water as the regenerating liquid. In order to facilitate the disposal of the regenerating or washing waste liquid, it is desirable to obtain concentration of contaminants within the liquid as high as possible, that is to obtain sulfuric acid of a concentration as high as possible. In order to obtain highly concentrated sulfuric acid, according to the conventional practices, a great number of washing tanks are provided and the washing is carried out repeatedly.
The sulfurous acid gas-adsorbing capacity of the adsorbent is sufficiently high during the initial stages, but with a lapse of time, the adsorbing capacity is lowered because the amount of adsorbed substance accumulated in the form of sulfuric acid increases. Accordingly, from the economical viewpoint it is reasonable to design the sulfurization apparatus so that the amount adsorbed per tank is small and the time for adsorption operation is shortened to repeat the adsorption and desorption many times over a short period of time.
As the volume of the gas to be treated increases, the number of beds of the adsorbent increases and the time for the adsorption is prolonged. Accordingly, it is reasonable to divide a great number of adsorbing beds into several series so as to conduct the adsorption and desorption in an appropriate time cycle and to perform the adsorption and desorption in each series according to the prescribed time schedule. However, in the conventional process and apparatus, a group of regenerating tanks are provided for each series, with the result that the size of the apparatus becomes extremely large and expensive, and correspondingly the construction and the maintenance of the apparatus is correspondingly a problem of considerable magnitude.